Wrigley Field casts a long shadow as prospective buyers review the Cubs’ confidential financial records and prepare the next round of bids for the stadium and team.

At issue is not whether the Cubs will remain at the beloved, 94-year-old ballpark, but how much it will cost to preserve and enhance Wrigley. The price that the franchise and stadium fetch will depend largely on how much more revenue can be wrung out of Wrigley.

“The franchise value is a guess on what future profits will be,” said Phillip Miller, an associate professor of economics at Minnesota State University-Mankato, who has studied baseball economics. “If you have to gut the place in the extreme case, that would affect the value.”

Bidders aren’t publicly discussing their plans for the stadium because the sales process is ongoing. But their concerns go beyond maintaining the stadium in a safe condition. Fans and players have expressed the desire for more modern amenities, such as a larger clubhouse and more space for concessions and bathrooms, without losing the vibe and charm of the old ballpark. If a new owner has to privately finance such improvements, fans could see higher ticket and food prices, and even the stadium’s sacrosanct name replaced with a corporate sponsor.

The costs of such extensive renovations could run into the hundreds of millions of dollars, an amount that could be a factor in negotiations if a new owner has to spend more than $1 billion, as some experts have estimated, to buy the package of the team, Wrigley Field and related broadcast properties.

But sources close to the bidders acknowledge that without a major ballpark restoration, new sources of revenue for the team are limited. In recent years, Tribune Co. has taken steps to generate more revenue by adding 1,800 bleacher seats, installing a lounge in the bleachers and putting advertising on the outfield doors.

“You can maintain Wrigley Field as is for a period of time,” said one source close to a bidder who did not want to be identified. “But the big question isn’t maintaining it. Whoever buys the team will have to make a gut check on what do you want the stadium to look like. The fact is there are revenue streams you can add to the stadium, but you got to build them first before you can charge for them.”

Cubs Chairman Crane Kenney said any improvements to Wrigley Field and their price tag “depends on how ambitious you are, how much you want to accomplish.” Otherwise, he added, “if you just maintain the place, you can play in Wrigley Field certainly though my lifetime, and I’m 46.”

Tribune Co. Chairman Sam Zell tried to remove some of the uncertainty about Wrigley Field by entertaining discussions with city and state officials about selling the ballpark to a state agency that owns the White Sox’s home. In the proposed deal, the Illinois Sports Finance Authority would have financed extensive renovations that would have included adding concessions and washrooms, building luxury suites and a club lounge. The estimated price tag: $300 million to $400 million.

Zell told prospective buyers that such a deal made good sense because it would have unloaded the burden of fixing Wrigley Field on the state. The deal also made sense for Zell. By selling the stadium separately, he hoped to get top dollar for the assets. Wringing the highest possible price is crucial for Tribune Co., which is weighed down by about $12 billion in debt, largely from Zell’s December deal to take the company private.

While the talks between Tribune Co., which owns the Chicago Tribune, and the state broke down in June, the idea of public stewardship of a landmark such as Wrigley Field is not out of the question. People familiar with past discussions don’t discount the possibility of a new team owner reopening negotiations with the state over how to finance a Wrigley face-lift. The state has an incentive to participate because Wrigley is one of Illinois’ biggest tourist attractions and the hub of a thriving North Side neighborhood.

Even with an antiquated facility, the Cubs are one of the most valuable franchises in Major League Baseball. Wrigley Field is a big reason for that. Even when the team is performing poorly, people pay for the ambience of watching a game in one of baseball’s oldest parks, with its ivy-covered walls and vintage scoreboard.

Tribune Co. does not publicly disclose the revenue and expenses generated by the ballpark. But the Chicago Tribune obtained a private appraisal of the stadium done in 2006, before recent improvements, that gives a peek inside the Wrigley cash cow. The Cubs also generate revenue outside of Wrigley, such as television contracts. A Tribune Co. spokesman declined to comment on the numbers.

In 2005, gross revenue from the sale of tickets reached $90.5 million, up from $62.4 million in 2003, an increase of 45 percent. In 2005, the Cubs sold 3.1 million tickets. Since then the team has increased seating capacity to about 42,000 from 39,538. Attendance broke 3.3 million this season.

The average concession revenue per capita has nearly doubled between 1995 and 2005, from $7.56 to $14.56.

Luxury suites are another source of revenue. Rental rates range from $110,000 to $167,000 a year for the 12-seat suites and $145,000 to $182,000 a year for the 15-seat suites. Wrigley has 67 original suites, according to the documents.

There’s no hiding the fact the park requires extensive upkeep. In 2005, the Cubs spent $4.9 million in major structural improvements and nearly $2 million more on operating expenses for regular maintenance and repairs at Wrigley. The $6.9 million outlay was more than double the $3.1 million the team spent on renovations and routine maintenance in 2003.

Maintenance expenses increased in 2005 after chunks of concrete fell from upper-deck panels on three occasions during the 2004 season. Based on recommendations of engineers, protective netting was installed to ensure the safety of the fans.

The engineering report found that “the upper-deck precast members should not require replacement in the near term (certainly not in the next 10 years).”

Three years after that report, Kenney said the stadium poses no safety risk. To maintain the structural soundness of the ballpark will not require a “very big capital outlay over the next 10 to 15 years,” he said, declining to disclose exact numbers.

Bidders, though, have hired their own engineers to inspect Wrigley Field and draw their own conclusions.

In presentations to prospective buyers, Cubs management has offered ideas to increase revenue from the existing real estate footprint. One possible new source of revenue that has been on the drawing board for a few years is a triangular-shaped building to be constructed on the player parking lot. The building would include parking, restaurants, player facilities and team offices.

“I see everything remaining to be done here as an opportunity,” Kenney said.

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